hook-development

Hook Development for DeepSeek Harness Plugins

Overview

Hooks are event-driven automation scripts that execute in response to DeepSeek Harness events. Use hooks to validate operations, enforce policies, add context, and integrate external tools into workflows.

Key capabilities:

• Validate tool calls before execution (PreToolUse)
• React to tool results (PostToolUse)
• Enforce completion standards (Stop, SubagentStop)
• Load project context (SessionStart)
• Automate workflows across the development lifecycle

Hook Types

Command Hooks (The Supported Type)

Execute bash commands for deterministic checks:

{
  "type": "command",
  "command": "bash ${PLUGIN_ROOT}/scripts/validate.sh",
  "timeout": 60
}

Use for:

• Fast deterministic validations
• File system operations
• External tool integrations
• Performance-critical checks

Hook Configuration Formats

Plugin hooks.json Format

For plugin hooks in com.deepseek.harness/hooks/hooks.json, use wrapper format:

{
  "description": "Brief explanation of hooks (optional)",
  "hooks": {
    "PreToolUse": [...],
    "Stop": [...],
    "SessionStart": [...]
  }
}

Key points:

• description field is optional
• hooks field is required wrapper containing actual hook events
• This is the plugin-specific format

Example:

{
  "description": "Validation hooks for code quality",
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write",
        "hooks": [
          {
            "type": "command",
            "command": "${PLUGIN_ROOT}/hooks/validate.sh"
          }
        ]
      }
    ]
  }
}

Settings Format (Direct)

For a standalone hook file (for example a project .agents/hooks/hooks.json), use the bare event-table format:

{
  "PreToolUse": [...],
  "Stop": [...],
  "SessionStart": [...]
}

Key points:

• No wrapper - events directly at top level
• No description field
• This is the settings format

Important: The examples below show the hook event structure that goes inside either format. For plugin hooks.json, wrap these in {"hooks": {...}}.